The naphthyridine derivatives (.+-.)-1,4-dihydro-5-isopropoxy-2-methyl-4-(2-trifluoromethylphenyl)-1,6-n aphthyridine-3-carboxylic acid ethyl ester ##STR1## and (.+-.)-1,4-dihydro-5-isopropoxy-2-methyl-4-(2-trifluoromethylphenyl)-1,6-n aphthyridine-3-carboxylic acid [2-(N-methyl-N-phenylmethylamino)-ethyl]ester ##STR2## are covered in Germany Patent Number 34 31 303 as highly effective calcium antagonists. U.S. Pat. Nos. 4,711,901, 4,760,081, and 4,751,228 are the corresponding patents and are incorporated herein by reference.